# std::get(std::pair)

From cppreference.com
< cpp‎ | utility‎ | pair

Defined in header `<utility>` |  |
template< std::size_t I, class T1, class T2 > typename std::tuple_element<I, std::pair<T1,T2> >::type& get( std::pair<T1, T2>& p ) noexcept; | (1) | (since C++11) (constexpr since C++14)
template< std::size_t I, class T1, class T2 > const typename std::tuple_element<I, std::pair<T1,T2> >::type& get( const std::pair<T1,T2>& p ) noexcept; | (2) | (since C++11) (constexpr since C++14)
template< std::size_t I, class T1, class T2 > typename std::tuple_element<I, std::pair<T1,T2> >::type&& get( std::pair<T1,T2>&& p ) noexcept; | (3) | (since C++11) (constexpr since C++14)
template< std::size_t I, class T1, class T2 > const typename std::tuple_element<I, std::pair<T1,T2> >::type&& get( const std::pair<T1,T2>&& p ) noexcept; | (4) | (since C++11) (constexpr since C++14)
template< class T, class U > constexpr T& get( std::pair<T, U>& p ) noexcept; | (5) | (since C++14)
template< class T, class U > constexpr const T& get( const std::pair<T, U>& p ) noexcept; | (6) | (since C++14)
template< class T, class U > constexpr T&& get( std::pair<T, U>&& p ) noexcept; | (7) | (since C++14)
template< class T, class U > constexpr const T&& get( const std::pair<T, U>&& p ) noexcept; | (8) | (since C++14)
template< class T, class U > constexpr T& get( std::pair<U, T>& p ) noexcept; | (9) | (since C++14)
template< class T, class U > constexpr const T& get( const std::pair<U, T>& p ) noexcept; | (10) | (since C++14)
template< class T, class U > constexpr T&& get( std::pair<U, T>&& p ) noexcept; | (11) | (since C++14)
template< class T, class U > constexpr const T&& get( const std::pair<U, T>&& p ) noexcept; | (12) | (since C++14)

Extracts an element from the pair using tuple-like interface.

1-4) The index-based overloads fail to compile if the index `I` is neither ​0​ nor 1.
5-12) The type-based overloads fail to compile if the types `T` and `U` are the same.

### Parameters

p | - | pair whose contents to extract

### Return value

1-4) Returns a reference to p.first if I == 0 and a reference to p.second if I == 1.
5-8) Returns a reference to p.first.
9-12) Returns a reference to p.second.

### Example

Run this code

    #include <iostream>
    #include <utility>

    int main()
    {
        auto p = std::make_pair(1, 3.14);
        std::cout << '(' << std::get<0>(p) << ", " << std::get<1>(p) << ")\n";
        std::cout << '(' << std::get<int>(p) << ", " << std::get<double>(p) << ")\n";
    }

Output:

    (1, 3.14)
    (1, 3.14)

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 2485 | C++11 (by index) C++14 (by type) | there are no overloads for const pair&& | the overloads are added

### See also

Structured binding (C++17) | binds the specified names to sub-objects or tuple elements of the initializer
get(std::tuple) (C++11) | tuple accesses specified element (function template)
get(std::array) (C++11) | accesses an element of an `array` (function template)
get(std::variant) (C++17) | reads the value of the variant given the index or the type (if the type is unique), throws on error (function template)
get(std::ranges::subrange) (C++20) | obtains iterator or sentinel from a std::ranges::subrange (function template)
get(std::complex) (C++26) | obtains a reference to real or imaginary part from a std::complex (function template)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/utility/pair/get&oldid=175379"